1. Field of the Invention
The present invention relates to an improvement of a detector for detecting a focusing state or a distance of a photographed object in which a light beam from the photographed object is received by a pair of light-receiving element arrays for detecting the focusing state or the distance of the photographed object, and the focusing state or the distance of the photographed object is detected by calculating an image shifting amount of image information in two systems outputted from the pair of light-receiving element arrays.
2. Description of the Related Art
In the focusing state or photographed object distance detector of this kind, image information obtained from two light-receiving element arrays are relatively shifted from each other to detect a discrete shifting amount having a highest correlation. An interpolating calculation is made on the basis of the discrete shifting amount. A continuous image shifting amount is calculated by performing interpolation using this interpolating calculated value so as to detect the focusing state or the distance of the photographed object.
In this case, there is a case in which an error in two image information is caused since an image is deformed by an error in A/D conversion, aberrations of an automatic focusing optical system, flare, etc. Such an error in two image information causes an error in image shifting amount.
Accordingly, in the general focusing state or photographed object distance detector, the focusing state or the distance of the photographed object is more accurately detected by using various kinds of methods.
For example, in Japanese Patent Application Laying Open (KOKAI) No. 62-205324, two light-receiving element arrays are arranged within a path of transmitted light in a photographing optical system such that these two light-receiving element arrays are symmetrically located with respect to a photographing optical axis. Each of the two light-receiving element arrays receives each of two symmetrical light beams transmitted through the photographing optical system. An interpolating calculation is made by using a correlational value of image signals from these two light-receiving element arrays and a contrast value of the photographed object. A reliable interpolating value with respect to a distance between two images is obtained by this interpolating calculation. Thus, the focusing state or the distance of the photographed object is detected with stable accuracy.
Japanese Patent Application Laying Open (KOKAI) No. 63-18312 shows a technique for detecting a focusing state or a distance of a photographed object similar to that shown in the above Japanese Patent Application Laying Open (KOKAI) No. 62-205324. In this technique, light beams are focused and formed as two images on two light-receiving element arrays through a photographing optical system. Contrast evaluating amounts are compared with each other in all ranges of relative displacements (or image shifts) of these two images. The focusings rate or the photographed object distance is more accurately detected by using a larger focusing contrast evaluating amount in calculation of an image shifting amount.
As mentioned above, in the general focusing state or photographed object distance detector, two image contrasts are used as parameters for performing a focusing operation, or contrast values are set to parameters when evaluated results of the image contrasts are judged, thereby improving a calculating accuracy. However, there is a limit in improvement of the calculating accuracy using such a method. Accordingly, it is desirable to improve the calculating accuracy by using another method, or detect the focusing state or the distance of the photographed object with high accuracy by using another method.